Jayboard, I've put about 10 more hours on the EH Fat Boys since I last posted. But first, what I like about the Svets is their full-roundedness. The highs are very natural with no shrillness. The bass booms impressively when it has to and there is no tubbiness--at least not in my system. I don't hear the congestion that you and Ckorody find in the mids. I'll listen more intently for it now--but it may be some time before I pull out the Fat Boys because I like them so much. The Fat Boys have an enveloping presence, subtle but palpable, that I'm very much enjoying. I listen to a lot of classical vocal music--solo and choral voices and opera--as well as a lot of chamber music and small combo jazz. I like a rich sounding mid range and lots of air around the voices and the instruments. The Fat Boys help to deliver that very well, along with sweet highs and reasonably good bass (deeper than the Svets I'm thinking thus far). Btw, the other tubes in the amp (a Jolida integrated), are Sylvania blackplate 5751 and Telefunken ECC 801S. The reason I didn't care so much for the regular EH EL34s is that they seemed a bit pallid in comparison to the Svets in the mid range and the bass didn't come alive as well. I realize that sounds subjective, but it's the best description I can give. Hope this helps.